Rivets vs Welding

[David Findlay]

I've not fully studied aircraft construction techniques so forgive me if the
answer to this is obvious. I've noted that most(if not all) aircraft made
with aluminium airframes seem to be riveted rather than welded. I'm not
sure about aircraft with composite or fibreglass skins so I won't be
dogmatic on that point, but anyway.

Is there a reason why aircraft would be riveted rather than welded together,
particularly on the airframe, not the skin? I would have imagined that
welding would produce a stronger join, although it may be harder or
impossible to disassemble if needed. Thanks,

David

[Matt Whiting]

Richard Riley wrote:

> That said, "friction stir welding" is the newest thing in airframe
> construction. It works below the melting temperature of the metal,
> and leaves good properties behind.

How does this work?


Matt

[David Findlay]

> How does this work?

http://en.wikipedia.org/wiki/Friction-stir_welding

Thanks,

David

[Matt Whiting]

David Findlay wrote:
>>How does this work?
>
>
> http://en.wikipedia.org/wiki/Friction-stir_welding
>
> Thanks,
>
> David

I found similar descriptions at The Welding Institute where the
technique was invented. However, I don't see any applications other
than for butt joints. I can see this being used for joining aircraft
skins, but I don't see how it can replace rivets for joining the skin to
internal support structures such as ribs and fuselage formers. Anyone
know if this is possible with this technique?


Matt

[David Findlay]

> So you'd have to weld the airplane together, then heat treat the
> entire thing.

Thanks, was pretty sure the must have been a reason, but not having looked
into it I didn't know.

> That said, "friction stir welding" is the newest thing in airframe
> construction. It works below the melting temperature of the metal,
> and leaves good properties behind.

I take it that this would be beyond the average home builder as yet though.

In terms of construction time and difficulty, how would composite compare to
aluminium riveted construction? Thanks,

David

[jc]

David Findlay wrote:

<snip>

> Is there a reason why aircraft would be riveted rather than welded
> together, particularly on the airframe, not the skin? I would have
> imagined that welding would produce a stronger join, although it may be
> harder or impossible to disassemble if needed. Thanks,

One key point is QC.

With the rivets a Al batch of a known alloy is turned into a bazillion
rivets by a machine. A small number of these rivets are tested to confirm
the batch of rivets is up to spec.

Using well understood and documented techniques a joint is designed for the
required stresses with x rows of rivets at y spacing etc. The joint is then
riveted.

QC on the joint itself merely requires visual examination, no fancy ND
techniques etc.

Routine inspection in service likewise is done by visual inspection.

--

regards

jc

LEGAL - I don't believe what I wrote and neither should you. Sobriety and/or
sanity of the author is not guaranteed

EMAIL - and are not valid email
addresses. news2x at perentie is valid for a while.

[Blueskies]

Check this out:

http://www.equitekcapital.com/Investorinfo/Webpagecontent/eclipse_articles/eclipseaeronews031104.htm


"Matt Whiting" > wrote in message ...
>
> I found similar descriptions at The Welding Institute where the technique was invented. However, I don't see any
> applications other than for butt joints. I can see this being used for joining aircraft skins, but I don't see how it
> can replace rivets for joining the skin to internal support structures such as ribs and fuselage formers. Anyone know
> if this is possible with this technique?
>
>
> Matt
>

[UltraJohn]

> So their overall costs are going to be a few percent below, say, the
> Cessna Citation Mustang.
>
> Competitively speaking, Cessna is in pretty good shape. They're very
> good at reducing the amount of labor in building an airplane. They
> have a large product line, experienced workers and plenty of capitol.
> They have long experience getting airplanes certified, that shouldn't
> be a problem. So if their cost on the Mustang is slightly higher,
> they're in good shape to price it with or below the Eclipse to
> preserve market share. If it's a price war between Cessna and
> Eclipse, which company can hold out longer? And if you were a
> corporate aviation buyer deciding between the two - and they were
> priced the same - would you buy a plane from a company that had no
> track record, or one that was very, very well established?
>
> Eclipse is dead, they just won't admit it yet.


Yes that's why even with the new engines there price is still about 1/3 the
price of the cessna, and they have over 2000 firm orders! Don't count them
out yet. Oh yeah their plane IS flying!
John

[Matt Whiting]

Richard Riley wrote:

> On Sun, 02 Jan 2005 01:33:54 GMT, UltraJohn
> > wrote:
>
> :
> :> So their overall costs are going to be a few percent below, say, the
> :> Cessna Citation Mustang.
> :>
> :> Competitively speaking, Cessna is in pretty good shape. They're very
> :> good at reducing the amount of labor in building an airplane. They
> :> have a large product line, experienced workers and plenty of capitol.
> :> They have long experience getting airplanes certified, that shouldn't
> :> be a problem. So if their cost on the Mustang is slightly higher,
> :> they're in good shape to price it with or below the Eclipse to
> :> preserve market share. If it's a price war between Cessna and
> :> Eclipse, which company can hold out longer? And if you were a
> :> corporate aviation buyer deciding between the two - and they were
> :> priced the same - would you buy a plane from a company that had no
> :> track record, or one that was very, very well established?
> :>
> :> Eclipse is dead, they just won't admit it yet.
> :
> :
> :Yes that's why even with the new engines there price is still about 1/3 the
> :price of the cessna, and they have over 2000 firm orders! Don't count them
> :out yet. Oh yeah their plane IS flying!
> :John
>
> Yes, their list is $1.175m. Do you believe that they are making any
> money at that price? I mean, it just about covers the cost of the
> engines and avionics.
>
> The orders are cancelable if they can't meet their price. They wont.
> Or Cessna will dramatically lower theirs. Cessna got about 350 orders
> in the first week after announcing.

And you can bet your bottom dollar that Cessna will make money on the
Mustang.


Matt

[Stealth Pilot]

On Sat, 01 Jan 2005 17:36:39 +1100, jc > wrote:

>David Findlay wrote:
>
><snip>
>
>> Is there a reason why aircraft would be riveted rather than welded
>> together, particularly on the airframe, not the skin? I would have
>> imagined that welding would produce a stronger join, although it may be
>> harder or impossible to disassemble if needed. Thanks,
>
>One key point is QC.
>
>With the rivets a Al batch of a known alloy is turned into a bazillion
>rivets by a machine. A small number of these rivets are tested to confirm
>the batch of rivets is up to spec.
>
>Using well understood and documented techniques a joint is designed for the
>required stresses with x rows of rivets at y spacing etc. The joint is then
>riveted.
>
>QC on the joint itself merely requires visual examination, no fancy ND
>techniques etc.
>
>Routine inspection in service likewise is done by visual inspection.

and in service a stuffed rivet can be merely drilled out and replaced.
a cracked weld would probably result in expensive repair, or the
resorting to rivetted in place patches.

rivets may not be the best in an ideal world but they are practical
and result in almost infinitely repairable aircraft.

david something that bears consideration is that over the full life of
an aircraft every component will come to need repair as it wears out.
so every component needs to be got at, removed, replaced or repaired
and put back into service. rivets may be tedious but allow this to
occur. welded components may lead to an entire airframe sitting on the
tarmac or in a hangar while repairs to cracks are thought through and
attempted.

australia's macchi jet trainers have cast ring beams in the fuselage
to which the wings attach. cracks in these saw lots of downtime while
repairs were contemplated and eventually led to the scrapping of the
aircraft. ...which isnt good for repeat business.

Stealth Pilot
Australia.

[UltraJohn]

Richard Riley wrote:

> On Sat, 01 Jan 2005 22:16:24 -0500, Matt Whiting
> > :>
> :> The orders are cancelable if they can't meet their price. They wont.
> :> Or Cessna will dramatically lower theirs. Cessna got about 350 orders
> :> in the first week after announcing.
> :
> :And you can bet your bottom dollar that Cessna will make money on the
> :Mustang.
>
> In the long run, absolutely. In the short run, if they have to take a
> loss on the Mustang to drive Eclipse under - I'll bet they'll do it.
I'm not stupid enough to bet money on any of them, butttt! if I had it I'd
probably buy the Columbia 400 <vbg>.
Sorry but it just irks me when someone (Richard) tries to drive down someone
who is trying to be innovative and really hasn't a clue as to their chance
of succeeding IMHO! But everyone is entitled to their opinions. I
personally hope they succeed even if I'll never be in a position to benefit
from it.

Happy New Year to everyone, even the ones I don't agree with <g>.
John

[David Findlay]

> david something that bears consideration is that over the full life of
> an aircraft every component will come to need repair as it wears out.
> so every component needs to be got at, removed, replaced or repaired
> and put back into service. rivets may be tedious but allow this to
> occur. welded components may lead to an entire airframe sitting on the
> tarmac or in a hangar while repairs to cracks are thought through and
> attempted.

I suppose part of that is to do with how long we operate aircraft. If
aircraft cost similiar to new cars and were similiar costs to maintain it
wouldn't matter if we threw out an airframe every 15-20 years, but at the
current costs it's rather impractical. Thanks,

David

[Matt Whiting]

Richard Riley wrote:
> On Sat, 01 Jan 2005 22:16:24 -0500, Matt Whiting
> > wrote:
> :>
> :> The orders are cancelable if they can't meet their price. They wont.
> :> Or Cessna will dramatically lower theirs. Cessna got about 350 orders
> :> in the first week after announcing.
> :
> :And you can bet your bottom dollar that Cessna will make money on the
> :Mustang.
>
> In the long run, absolutely. In the short run, if they have to take a
> loss on the Mustang to drive Eclipse under - I'll bet they'll do it.

That's part of making money! :-)

Matt

[Kyle Boatright]

"UltraJohn" > wrote in message
link.net...
> Richard Riley wrote:
>
>> On Sat, 01 Jan 2005 22:16:24 -0500, Matt Whiting
>> > :>
>> :> The orders are cancelable if they can't meet their price. They wont.
>> :> Or Cessna will dramatically lower theirs. Cessna got about 350 orders
>> :> in the first week after announcing.
>> :
>> :And you can bet your bottom dollar that Cessna will make money on the
>> :Mustang.
>>
>> In the long run, absolutely. In the short run, if they have to take a
>> loss on the Mustang to drive Eclipse under - I'll bet they'll do it.
> I'm not stupid enough to bet money on any of them, butttt! if I had it I'd
> probably buy the Columbia 400 <vbg>.
> Sorry but it just irks me when someone (Richard) tries to drive down
> someone
> who is trying to be innovative and really hasn't a clue as to their chance
> of succeeding IMHO! But everyone is entitled to their opinions. I
> personally hope they succeed even if I'll never be in a position to
> benefit
> from it.
>
> Happy New Year to everyone, even the ones I don't agree with <g>.
> John

No need to get irked. Just present your opinion, particularly if it is
better reasoned.

Personally, I didn't think Cirrus had much of a chance when they got in the
certified business, but they found a niche and are doing quite well there.
Maybe Eclipse or another of the small jet makers will do just as well. Only
time will tell.

KB

[John Halpenny]

David Findlay wrote:
> =

> > david something that bears consideration is that over the full life o=
f
> > an aircraft every component will come to need repair as it wears out.=

> > so every component needs to be got at, removed, replaced or repaired
> > and put back into service. rivets may be tedious but allow this to
> > occur. welded components may lead to an entire airframe sitting on th=
e
> > tarmac or in a hangar while repairs to cracks are thought through and=

> > attempted.
> =

> I suppose part of that is to do with how long we operate aircraft. If
> aircraft cost similiar to new cars and were similiar costs to maintain =
it
> wouldn't matter if we threw out an airframe every 15-20 years, but at t=
he
> current costs it's rather impractical. Thanks,
> =

> David

A century ago, people traveled by ship or train, both of which were held
together with rivets. Sometimes in the 1940's they both switched to
welding, and soon after the passengers switched to planes and busses,
both of which still use rivets. Coincidence? =

-- =

John Halpenny


A cluttered desk is the sign of a cluttered mind.
I=92m so glad my desk isn't empty.

[Matt Whiting]

John Halpenny wrote:

> David Findlay wrote:
>
>>>david something that bears consideration is that over the full life of
>>>an aircraft every component will come to need repair as it wears out.
>>>so every component needs to be got at, removed, replaced or repaired
>>>and put back into service. rivets may be tedious but allow this to
>>>occur. welded components may lead to an entire airframe sitting on the
>>>tarmac or in a hangar while repairs to cracks are thought through and
>>>attempted.
>>
>>I suppose part of that is to do with how long we operate aircraft. If
>>aircraft cost similiar to new cars and were similiar costs to maintain it
>>wouldn't matter if we threw out an airframe every 15-20 years, but at the
>>current costs it's rather impractical. Thanks,
>>
>>David
>
>
> A century ago, people traveled by ship or train, both of which were held
> together with rivets. Sometimes in the 1940's they both switched to
> welding, and soon after the passengers switched to planes and busses,
> both of which still use rivets. Coincidence?

Uh, yes. :-)


Matt